Method for making incandescent lamps



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METHOD FOR MAKING INCANDESCENT LAMPS Filed June 10, 1960 FIG.I. v F162. Fae. 5.

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HTTO/FA/EX United States Patent 3,271,093 METHOD FOR MAKING INCANDESCENT LAMPS Arthur P. Meier, Bloomfield, N.J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed June 10, 1960, Ser. No. 35,360 2 Claims. (Cl. 316-19) This invention relates to incandescent lamps and, more particularly, to an improved method of making same.

For some types of incandescent electric lamps, it is desirable to orient the filament so that it generally parallels the axis of the lamp envelope. It is known to mount a coiled filament in such a manner by supporting it between two conducting leads of different lengths. When such lamps are subjected to vibrational stresses, the longer supporting conducting lead displays some tendency for excessive whip or vibration. It is also known to provide double-ended lamps with relatively short conducting leads positioned at each end of the lamp, with the filament mounted therebetween. While such shorter conducting leads minimize vibration effects, additional difficulties are introduced with respect to mounting the filament.

It is the general object of this invention to avoid and overcome the foregoing and other difllculties of and objections to prior-art practices by providing an improved method for making an incandescent lamp wherein the coiled filament generally parallels the envelope axis.

It is another object to provide an improved method for making an incandescent lamp which has good vibration resistance and is simple to manufacture and wherein the coiled filament generally parallels the envelope axis.

The aforesaid objects of the invention, and other objects which will become apparent as the description proceeds, are achieved by providing a method for making an incandescent lamp which comprises a sealed envelope with a pair of conducting leads supported proximate one end of the envelope. One of the conductingleads is relatively short and extends into and terminates within the envelope. The other conducting lead is relative-1y long and extends throughout the length of the envelope. This long lead is supported proximate both ends of the envelope. The long conducting lead is provided with a bent section which is disposed generally transverse the axis defined by the ends of the envelope. A coiled filament is supported between the bent section of the long conducting lead and the inwardly-extending extremity of the short conducting lead. These individual leads are adapted to have an energizing electric potential applied thereacross. In the method for making such a lamp, the filament is placed under a predetermined tension after it is mounted in the lamp and is maintained under such predeterminetd tension by the relative positioning of the supporting conducting leads.

For a better understanding of the invention, reference should be had to the accompanying drawings wherein:

FIG. 1 is an elevational view, partly in section, of a completed lamp constructed in accordance with the present invention.

FIG. 2 is an elevational View of a completed mount structure which represents an initial step in the lamp manufacture;

FIG. 3 is an elevational view, partly in section, wherein a mount as shown in FIG. 2 is inserted into a doubleended envelope;

FIG. 4 is a top view of the partially fabricated lamp as shown in FIG. 3;

FIG. 5 illustrates a further step in the lamp manufacture, wherein selected portions of both conducting leads are sealed into the lamp envelope proximate one end thereof;

FIG. 6 is an elevational view, partly in section, wherein the filament is placed under a predetermined tension while the longer conducting lead is sealed into an end of the lamp envelope.

While the principles of the invention are broadly applicable to any incandescent lamp and the method of manufacturing such a lamp, the invention is conveniently employed in the construction and manufacture of doubleended miniature lamps which are fabricated with a buttseal construction, and hence it has been so illustrated and will be so described.

With specific reference to the form of the invention illustrated in the drawings, the lamp 10 as shown in FIG. 1 generally comprises a vitreous, radiation-transmitting envelope 12 which preferably has a generally tubular configuration. A relatively short first conducting lead 14 and a relatively long second conducting lead 16 are both supported proximate one end of the envelope 12, preferably by means of a mounting bead 18 and by the conventional butt-seal lamp construction, wherein the conducting leads l4 and 16 are supported by and are sealed into an end of the envelope 12. The relatively short conducting lead 14 extends into and terminates within the envelope 12 and preferably the inwardly extending extremity 20 of the first conducting lead 14 is bent generally transverse to the axis defined by the ends of the envelope 12, in order to facilitate filament mounting. The relatively long conducting lead 16 extends throughout the length of the envelope and is supported proximate both envelope ends. The second conducting lead 16 also has a resilient bent section 22 which is disposed generally transverse to the envelope axis, and preferably at an angle of about with respect to the en velope axis. A coiled filament 24 is supported between the bent section 22 of the second conducting lead 16 and the first conducting lead 14 proximate its inwardly extending extremity 20. The first and second conducting leads are adapted to have an electric potential applied thereacross and are connected to conventional metallic contact adaptors 26 and 28 attached to both ends of the envelope 12. In the preferred form of the lamp, the conducting lead 14 electrically connects to the contact adaptor 26 and the conducting lead 16 electrically connects to the contact adaptor 28.

In the manufacture of the lamp as shown in FIG. 1, the filament mount structure 30 is first fabricated as shown in FIG. 2. In forming this filament mount 30, the relatively short conducting lead 14 is supported in spaced and generally parallel relationship with [respect to the relatively long second conducting lead 16 by means of the mounting bead 18. The resilient bent section 22 of the second conducting lead 16 is also positioned in predetermined spaced relationship from the closest extremity 20 of the first conducting lead 14 and a coiled filament 24 of predetermined dimensions is mounted between the bent section 22 of the second conducting lead and the closest extremity 20 of the first conducting lead. The lead bent section 22 is generally transverse to adjacent portions of the lead 16.

In the next step of the lamp manufacture as shown in FIGS. 3 and 4, the mount structure 30 is inserted into an open-ended vitreous envelope 12, which preferably has a generally-tubular configuration. The dimensions of the mount structure 30 and the envelope 12 are selected so that an extremity portion 32 of the first conducting lead 14 projects from one end of the envelope and extremity portions 34 and 34a of the second conducting lead 16 project from both ends of the envelope 12, with the filament 24 positioned entirely within the envelope 12.

In the following step of lamp manufacture as shown in FIG. 5, the end of an additional vitreous tubulation 36 is heated to its softening temperature, as is that end of the envelope which has extremity portions of both conducting leads passing therethrough. The heated vitreous tubulation 36 and the envelope end are pressed together in order to seal into the envelope the selected extremity portions 32 and 34 of both conducting leads 14 and 16. This manufacturing step is conventional for a so-called butt-sealed lamp construction and serves to seal the mount 30 into one end of the envelope 12. As is also usual in such lamp construction, an additional constricted area 38 is desirably provided in a tubulation 36, in order to permit the tubulation to be tipped off and sealed during a later step of lamp manufacture.

Following sealing of the mount 30 into one end of the envelope 12, a predetermined tension is applied proximate the free or unsealed end portion 34a of the conducting lead 16, as is shown in FIG. 6. This causes the bent section 22 of the lead 16 to fiex a predetermined amount and places a predetermined tension on the filament 24. As a specific example, with a coiled tungsten filament having 196 turns per inch and a total of 42 turns, a wire diameter of 2.83 mils and a barrel diameter of 16.9 mils, the lead wire 16 is moved a total distance of 1.5 mm. to stretch the filament about 0.8 mm. While the lead 16 is maintained under tension, the unsealed end of the envelope 12, through which the still-free extremity 34a of the conducting lead 16 passes, is heated in a conventional manner with a gas flame 40 to sea-l the conducting lead 16 therein. Thereafter oxygen is removed in conventional fashion from the envelope 12 and it is hermetically sealed by tipping off the tubulation 36 at its constricted portion 38. To complete the lamp manufacture, the portions of the lead conductors 14 and 16 which project from the lamp are electrically connected to conventional contact adaptors 26 and 28, which are afiixed to the ends of the envelope 12 by means of cement.

The foregoing lamp is extremely simple to manufacture and tensioning of the filament is readily accomplished by appliying a predetermined tension on the free end of the conducting lead 16 to move it a predetermined amount. 16, which is used to support one end of the filament 24, is supported proximate both ends of the envelope, thereby minimizing the effects of vibration on lamp performance, which are particularly noticeable with longer unsupported conducting leads.

The foregoing lamp is subject to considerable modification. As an example, while the lamp construction as described is particular-ly suited to a butt-seal type of lamp, the butt seal could be replaced by the well-known flaretype lamp construction. In addition, while a doubleended lamp has been shown with contact adaptors connecting to both envelope ends, the lamp as shown in FIG. 1 could be readily modified by eliminating the electrical contact adaptor 28 and connecting both leads to the contact adaptor 26.

As another possible alternative method of manufacture, the lead conductor 16 could be bent at predetermined amount before the mount 30 is inserted into the envelope 12, in order to place a predetermined tension on the filament. This would eliminate the necessity for tensioning the free end of the lead conductor 16 while sealing it into the lamp envelope. It is preferred to fabricate the lamp by the preferred method as described, however, since tensioning the filament 24 while sealing the longer lead conductor 16 into the end of the envelope 12 eliminates any tendency for spring-back of the bent section 22 of the conducting lead 16, thereby making filament tensioning more accurate and positive.

In addition, the relatively long conducting lead It will be recognized that the objects of the invention have been achieved by providing an improved method for making an incandescent lamp wherein the coiled filament generally parallels the envelope axis. This lamp has good resistance to vibration and is simple to manufacture.

While the best embodiment of the invention has been illustrated and described. in detail, it is to be particularly understood that the invention is not limited thereto or thereby.

I claim:

1. The method of sealing an incandescible filament under predetermined tension within an envelope, which method comprises: supporting a relatively short first conducting lead in spaced and generally parallel relationship with respect to a relatively long second conducting lead having a resilient section bent generally transverse to adjacent conducting lead portions, and positioning in predetermined spaced relationship the bent section of said second conducting lead and the closest extremity of said first conducting lead; connecting a filament of predeterminted dimensions between the bent section of said second conducting lead and said first conducting lead proximate its positioned extremity; inserting into an open-ended vitreous envelope said supported conducting leads and said filament, with portions of both said first and second conducting leads projecting from one envelope end and only a portion of said second conducting lead projecting from the other envelope end; sealing into one selected end of said envelope portions of both said first and second conducting leads as project through such selected envelope end; applying a predetermined tension on said second conducting lead to cause the bent section thereof to flex a predetermined amount to place a predetermined tension on said filament; sealing the other end of said envelope about the second conducting lead portion projecting therethrough while maintaining the predetermined tension on said second conducting lead; and removing oxygen from said envelope and hermetically sealing same.

2. The method as specified in claim 1, wherein both said conducting lead portions which project through one envelope end are sealed therein by first heating such envelope end to soften same, and thereafter forcing an end of a vitreous tubulation heated to its softening temperature against such heated envelope end to seal both projecting conducting lead portions therebetween.

References Cited by the Examiner UNITED STATES PATENTS 985,422 2/1911 Knight 313-274 1,869,998 8/1932 Cartun 313274 2,191,346 2/1940 Greimer 313274 2,338,6'21 1/1944 Carter 313274 2,565,138 8/1951 Leighton 313274 X 2,692,350 10/1954 Arnott 313207 X 2,938,137 5/1960 Roger et a1. 3l3-307 X 3,007,074 10/1961 Swasey et al. 313277 X 3,013,169 12/1961 Gungle et a1 313-42 HERMAN KARL SAALBACH, Primary Examiner.

RALPH G. NILSON, ARTHUR GAUSS, GEORGE N. WESTBY, Examiners.

I. I. MCCORMACK, S. CHATMON,

Assistant Examiners. 

1. THE METHOD OF SEALING AN INCANDESCIBLE FILAMENT UNDER PREDETERMINED TENSION WITHIN AN ENVELOPE, WHICH METHOD COMPRISES: SUPPORTING A RELATIVELY SHORT FIRST CONDUCTING LEAD IN SPACED AND GENERALLY PARALLEL RELATIONSHIP WITH RESPECT TO A RELATIVELY LONG SECOND CONDUCTING LEAD HAVING A RESILIENT SECTION BENT GENERALLY TRANSVERSE TO ADJACENT CONDUCTING LEAD PORTIONS, AND POSITIONING IN PREDETERMINED SPACED RELATIONSHIP THE BENT SECTION OF SAID SECOND CONDUCTING LEAD AND THE CLOSEST EXTREMITY OF SAID FIRST CONDUCTING LEAD; CONNECTING A FILAMENT OF PREDETERMINED DIMENSIONS BETWEEN THE BENT SECTION OF SAID SECOND CONDUCTING LEAD AND SAID FIRST CONDUCTING LEAD PROXIMATE ITS POSITIONED EXTREMITY; INSERTING INTO AN OPEN-ENDED VITREOUS ENVELOPE SAID SUPPORTED CONDUCTING LEADS AND SAID FILAMENT, WITH PORTIONS OF BOTH SAID FIRST AND SECOND CONDUCTING LEADS PROJECTING FROM ONE ENVELOPE END AND ONLY A PORTION OF SAID SECOND CONDUCTING LEAD PROJECTING FROM THE OTHER ENVELOPE END; SEALING INTO ONE SELECTED END OF SAID ENVELOPE PORTIONS OF BOTH SAID FIRST AND SECOND CONDUCTING LEADS AS PROJECT THROUGH SUCH SELECTED ENVELOPE END; APPLYING A PREDETERMINED TENSION ON SAID SECOND CONDUCTING LEAD TO CAUSE THE BENT SECTION THEREOF TO FLEX A PREDETERMINED AMOUNT TO PLACE A PREDETERMINED TENSION ON SAID FILAMENT; SEALING THE OTHER END OF SAID ENVELOPE ABOUT THE SECOND CONDUCTING LEAD PORTION PROJECTING THERETHROUGH WHILE MAINTAINING THE PREDETERMINED TENSION ON SAID SECOND CONDUCTING LEAD; AND REMOVING OXYGEN FROM SAID ENVELOPE AND HERMETICALLY SEALING SAME. 